Sound transmission between floors and walls is a common source of complaint from homeowners and condo dwellers. In private homes, it’s an issue of isolating the sound from, for example, home theatres from sleep and quiet areas.
In multi-unit buildings, it can result in heated disputes within condo boards regarding privacy and lifestyle, perhaps even leading to litigation. Sound-reflective interior design trends that currently lean towards hard floors surfaces and minimalist features can make the matter even more of a frustration to all residents.
The issue of sound transmission should be addressed prior to construction or renovation. In fact, the National Building Code mandates a sound transmission class rating [STC] between walls and floors of at least 50. Some provinces and municipalities require STC ratings as high as 55. The issue for many builders, however, is that code minimum wall and ceiling assembly requirements have not kept pace with the STC requirements, resulting in walls and ceilings that are far below the STC 50 level. Therefore, architects, builders and developers need to be more proactive when it comes to sound mitigation. According to one industry expert, moving up five or 10 STCs can mean more than doubling the soundproofing.
The possible solutions for dealing with sound transmission can be summarized in four words: absorption, mass, decoupling and dampening. For example, an un-insulated two-by-four wood or metal stud wall with gypsum board on each side has an STC rating of only 15. Stuff some fibreglass insulation between the studs and the absorption factor increases to an STC of 38 for wood studs and 45 for metal. However, even added mass on its own can help — a second layer of gypsum on each side of an insulated wall raises the STC to 40. However, these all fall short of code STC requirements.
To reach the next level of soundproofing, some sound experts recommend using resilient metal channels installed on the stud or concrete walls underneath the gypsum board in order to de-couple and divide the hard surfaces. Other products that act as clips or rubber shock absorbers are also available. Noise-reducing laminated core gypsum board is also available, which not only reduces sound transmission but represents a one-step process that reduces installation time.
Sound dampening products can also effectively deal not only with sound transmission between walls but between floors. Canadian-made SONOPAN from MSL in Louisville, Que., is a patented sound insulation panel that has been available for 20 years in its home province and is now being distributed across Canada. Made from 100 per cent recycled wood (ie. eligible for LEED points), SONOPAN is easy to install and can be used on both walls and ceilings before or after construction to deliver STC gains that exceed code requirements.
Attempts to improve soundproofing after construction can cost tens of thousands of dollars for builders who find themselves tangled up in a post-construction dispute with a homeowner or condo board. However, if taken into account during the building envelope design phase, the added cost may not be significant, given for example the R-value that the 19-millimetre-thick SONOPAN panel itself contributes.
Even so, the investment made to improve soundproofing beyond code minimum can be a positive marketing message for builders and developers at a time when privacy and quiet has become an increasingly important factor for consumers. Of course, anyone can claim their project is as silent as a mouse. However, by hiring an acoustician as a member of the design team and making their report available to prospective buyers, one can establish their commitment to the sound of silence.
John Bleasby is a Coldwater, Ont. based freelance writer. Send comments and Inside Innovation column ideas to email@example.com